Västervik statement: https://www.facebook.com/permalink.php?story_fbid=pfbid0p5DPeaPvD9MDExcB4bRrSp7wJVY6t83KJSSty3oPAoJh9rrJzrbZbTCP4zeohhnQl&id=100048530876966
Basically they use a fixed size håltolk ( plug gauge?). According to Västervik it was noticed that the gauge fit into the carburettors
(=they were believed to be too big)which never happened before.At that point the race management was brought in and the faulty carburettors
was locked in for further investigation. The carburettors was brought to manufacturer Mikael Blixt measured them and according to him the carburettors were not oversized
According to Blixt and Indianerna carburettor sizes were (in millimetres and I assume limit is 34 mm):
34,051
34,100
33,960
33,990
Also to answer your question #2 @stewmac I don't know but I don't think every bike/engine is checked, but rather random check.
[speculation] It could be that someone was suspicious of Kowalski's engines and wanted them checked, isn't be the first time
someone wants an opponent bike checked.